Monitoring device for laser light cable has third electrical circuit for monitoring capacitance between inner and outer metal casings in addition to first and second monitoring circuits

摘要

The laser light cable (2) has an optical fiber, an inner metal casing (7) enclosing the optical fiber, an insulating envelope enclosing the inner casing and an outer metal casing (9). The device has a first electric circuit (13) for monitoring a circuit containing the inner metal casing and a second circuit (14) for monitoring the resistance between the inner and outer metal casings. There is a third electrical circuit (15) for monitoring the capacitance between the inner and outer metal casings.